1
LT1780/LT1781
Low Power 5V RS232
Dual Driver/Receiver with
±15kV ESD Protection
TransZorb is a registered trademark of General Instruments, GSI.
R
Output Waveforms
1780/81 • TA02
DRIVER
OUTPUT
R
L
= 3k
C
L
= 2500pF
RECEIVER
OUTPUT
C
L
= 50pF
INPUT
0.1µF
0.1µF
0.1µF
0.1µF
LOGIC
INPUTS
LOGIC
OUTPUTS
ON/OFF 18
10
13
11
12
6
5
4
2
16
9
14
8
15
7
3
17 5V INPUT
V+ OUT
V– OUT
RS232 OUTPUT
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
1780/81 • TA01
5k
5k
LT1780
U
A
O
PPLICATITYPICAL
S
FEATURE
D
U
ESCRIPTIO
The LT
®
1780/LT1781 are dual RS232 driver/receiver pairs
with integral charge pump to generate RS232 voltage
levels from a single 5V supply. Using only 0.1µF external
capacitors, these circuits consume only 40mW of power,
and can operate to 120kbaud even while driving heavy
capacitive loads. New ESD structures on the chip allow the
LT1780/LT1781 to survive ±15kV air gap and ±8kV con-
tact ESD tests per IEC 1000-4-2, eliminating the need for
costly TransZorbs
®
on the RS232 line pins. The LT1780/
LT1781 are fully compliant with EIA RS232 standards.
Driver outputs are protected from overload, and can be
shorted to ground or up to ±30V without damage. During
SHUTDOWN or power-off conditions, driver and receiver
outputs are in a high impedance state, allowing line
sharing.
The LT1780/LT1781 are direct upgrades to the LT1180A/
LT1181A, LT1280A/LT1281A and LT1381 for applications
which require the utmost ESD protection.
The LT1781 is available in 16-pin DIP,SO and SW pack-
ages. The LT1780 is supplied in 18-pin DIP and SW
packages for applications which require SHUTDOWN.
■
10mA Max Supply Current
■
ESD Protection to IEC 1000-4-2 Level 4
±
15kV Air Gap,
±
8kV Contact
■
Uses Small Capacitors: 0.1
µ
F
■
120kBaud Operation for R
L
= 3k, C
L
= 2500pF
■
250kBaud Operation for R
L
= 3k, C
L
= 1000pF
■
Outputs Withstand ±30V Without Damage
■
CMOS Comparable Low Power: 40mW
■
Operates from a Single 5V Supply
■
Rugged Bipolar Design
■
Outputs Assume a High Impedance State When Off
or Powered Down
■
Meets All RS232 Specifications
■
Available With or Without Shutdown
■
Absolutely No Latch-up
■
Portable Computers
■
Battery-Powered Systems
■
Power Supply Generator
■
Terminals
■
Modems
U
S
A
O
PPLICATI
, LTC and LT are registered trademarks of Linear Technology Corporation.
2
LT1780/LT1781
A
U
G
W
A
W
U
W
ARBSOLUTEXI T
I
S
Supply Voltage (V
CC
) ................................................ 6V
V
+
........................................................................ 13.2V
V
–
...................................................................... –13.2V
Input Voltage
Driver ........................................................... V
–
to V
+
Receiver ............................................... – 30V to 30V
ON/OFF ................................................. –0.3V to 12V
Output Voltage
Driver ...................................... V
+
– 30V to V
–
+ 30V
Receiver .................................... – 0.3V to V
CC
+ 0.3V
Short-Circuit Duration
V
+
................................................................... 30 sec
V
–
................................................................... 30 sec
Driver Output.............................................. Indefinite
Receiver Output.......................................... Indefinite
Operating Temperature Range ..................... 0°C to 70°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
WU
U
PACKAGE/ORDER I FOR ATIO
ORDER
PART
NUMBER
ORDER
PART
NUMBER
LT1780CN
LT1780CSW LT1781CN
LT1781CS
LT1781CSW
(Note 2)
ELECTRICAL C CHARA TERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Power Supply Generator
V
+
Output 7.9 V
V
–
Output –7 V
Supply Current (V
CC
) (Note 3), T
A
= 25°C 8 10 mA
●14 mA
Supply Current When OFF (V
CC
) SHUTDOWN (Note 4) LT1780 Only ●110 µA
Supply Rise Time C1 = C2 = C3 = C4 = 0.1µF 0.2 ms
SHUTDOWN to Turn-On LT1780 Only 0.2 ms
ON/OFF Pin Thresholds Input Low Level (Device SHUTDOWN) ●0.8 1.2 V
Input High Level (Device Enabled) ●1.6 2.4 V
ON/OFF Pin Current 0V ≤ V
ON/OFF
≤ 5V ●–15 80 µA
Oscillator Frequency 130 kHz
Driver
Output Voltage Swing Load = 3k to GND Positive ●5.0 7.5 V
Negative ●–6.3 –5 V
Logic Input Voltage Level Input Low Level (V
OUT
= High) ●1.4 0.8 V
Input High Level (V
OUT
= Low) ●2.0 1.4 V
1
2
3
4
5
6
7
8
9
TOP VIEW
18
17
16
15
14
13
12
11
10
NC
C1
+
V
+
C1
–
C2
+
C2
–
V
–
TR2 OUT
REC2 IN
N PACKAGE
18-LEAD PLASTIC DIP
ON/OFF
V
CC
GND
TR1 OUT
REC1 IN
REC1 OUT
TR1 IN
TR2 IN
REC2 OUT
SW PACKAGE
18-LEAD PLASTIC SO
T
JMAX
= 125°C, θ
JA
= 80°C/W, θ
JC
= 36°C/W (N)
T
JMAX
= 125°C, θ
JA
= 90°C/ W, θ
JC
= 26°C/W (SW)
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
C1
+
V
+
C1
–
C2
+
C2
–
V
–
TR2 OUT
REC2 IN
V
CC
GND
TR1 OUT
REC1 IN
REC1 OUT
TR1 IN
TR2 IN
REC2 OUT
N PACKAGE
16-LEAD PLASTIC DIP S PACKAGE
16-LEAD PLASTIC SO SW PACKAGE
16-LEAD PLASTIC SO
T
JMAX
= 125°C, θ
JA
= 90°C/W, θ
JC
= 46°C/W (N)
T
JMAX
= 125°C, θ
JA
= 95°C/W, θ
JC
= 34°C/W (S)
T
JMAX
= 125°C, θ
JA
= 95°C/ W, θ
JC
= 27°C/W (SW)
Consult factory for Industrial and Military grade parts.
(Note 1)
3
LT1780/LT1781
ELECTRICAL C CHARA TERISTICS
(Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Logic Input Current 0.8V ≤ V
IN
≤ 2.0V ●520 µA
Output Short-Circuit Current V
OUT
= 0V ±717 mA
Output Leakage Current SHUTDOWN V
OUT
= ±30V (Note 4) ●10 100 µA
Data Rate R
L
= 3k, C
L
= 2500pF 120 kBaud
R
L
= 3k, C
L
= 1000pF 250 kBaud
Slew Rate R
L
= 3k, C
L
= 51pF 15 30 V/µs
R
L
= 3k, C
L
= 2500pF 4 7 V/µs
Propagation Delay Output Transition t
HL
High-to-Low (Note 5) 0.6 1.3 µs
Output Transition t
LH
Low-to-High 0.5 1.3 µs
Receiver
Input Voltage Thresholds Input Low Threshold (V
OUT
= High) 0.8 1.3 V
Input High Threshold (V
OUT
= Low) 1.7 2.4 V
Hysteresis ●0.1 0.4 1 V
Input Resistance V
IN
= ±10V 357 kΩ
Output Leakage Current SHUTDOWN (Note 4) 0 ≤ V
OUT
≤ V
CC
●110 µA
Output Voltage Output Low, I
OUT
= –1.6mA ●0.2 0.4 V
Output High, I
OUT
= 160µA (V
CC
= 5V) ●3.5 4.2 V
Output Short-Circuit Current Sinking Current, V
OUT
= V
CC
–10 mA
Sourcing Current, V
OUT
= 0V 10 20 mA
Propagation Delay Output Transition t
HL
High-to-Low (Note 6) 250 600 ns
Output Transition t
LH
Low-to-High 350 600 ns
Note 4: Supply current measurements in SHUTDOWN are performed with
V
ON/OFF
≤ 0.1V.
Note 5: For driver delay measurements, R
L
= 3k and C
L
= 51pF. Trigger
points are set between the driver’s input logic threshold and the output
transition to the zero crossing (t
HL
= 1.4V to 0V and t
LH
= 1.4V to 0V).
Note 6: For receiver delay measurements, C
L
= 51pF. Trigger points are
set between the receiver’s input logic threshold and the output transition
to standard TTL/CMOS logic threshold (t
HL
= 1.3V to 2.4V and t
LH
= 1.7V
to 0.8V).
The ● denotes specifications which apply over the operating temperature
range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Testing done at V
CC
= 5V and V
ON/OFF
= 3V, unless otherwise
specified.
Note 3: Supply current is measured as the average over several charge
pump cycles. C
+
= C
–
= C1 = C2 = 0.1µF. All outputs are open, with all
driver inputs tied high.
–20
4
LT1780/LT1781
CCHARA TERISTICS
UW
AT
Y
P
I
CALPER
F
O
RC
E
Receiver Input Thresholds
ON/OFF Thresholds
TEMPERATURE (°C)
–55
0.50
THRESHOLD VOLTAGE (V)
0.75
1.25
1.50
1.75
3.00
2.25
050 75
1780 • G04
1.00
2.50
2.75
2.00
–25 25 100 125
INPUT HIGH
INPUT LOW
DATA RATE (kBAUD)
0
0
SUPPLY CURRENT (mA)
10
20
30
40
50
25 50 75 100
1780 • G05
125 150
2 DRIVERS ACTIVE
RL = 3k
CL = 2500pF
Supply Current vs Data Rate
TEMPERATURE (°C)
–55
THRESHOLD VOLTAGE (V)
2.0
2.5
3.0
25 75
1780 • G06
1.5
1.0
–25 0 50 100 125
0.5
0
ON THRESHOLD
OFF THRESHOLD
Supply Current
TEMPERATURE (°C)
–55
0
SUPPLY CURRENT (mA)
10
25
050 75
1780 • G07
5
20
15
–25 25 100 125
2 DRIVERS LOADED R
L
= 3k
1 DRIVER LOADED R
L
= 3k
NO LOAD
Driver Output Voltage
Driver Minimum Output Voltage
vs Load Capacitance
Driver Maximum Output Voltage
vs Load Capacitance
LOAD CAPACITANCE (nF)
0
5.0
PEAK OUTPUT VOLTAGE (V)
5.5
6.0
6.5
7.0
7.5
8.0
2468
1780 • G01
1013579
20k BAUD
60k BAUD
120k BAUD
LOAD CAPACITANCE (nF)
0
–7.0
PEAK OUTPUT VOLTAGE (V)
–6.5
–6.0
–5.5
–5.0
–4.5
–4.0
2468
1780 • G02
1013579
120k BAUD
60k BAUD
20k BAUD
TEMPERATURE (°C)
–55
–10
DRIVER OUTPUT VOLTAGE (V)
–8
–4
–2
0
10
4
050 75
1780 • G03
–6
6
8
2
–25 25 100 125
OUTPUT HIGH
OUTPUT LOW
R
L
= 3k
V
CC
= 5V
V
CC
= 4.5V
V
CC
= 5.5V
V
CC
= 4.5V
V
CC
= 5V
V
CC
= 5.5V
5
LT1780/LT1781
CCHARA TERISTICS
UW
AT
Y
P
I
CALPER
F
O
RC
E
Shutdown to Driver Outputs Driver Output Waveforms
1780 • G13
1780 • G12
INPUT
DRIVER OUTPUT
R
L
= 3k
DRIVER OUTPUT
R
L
= 3k
C
L
= 2500pF
10V
5V
GND
DRIVER 1
OUTPUT
DRIVER 2
OUTPUT
ON/OFF PIN
GND
–10V
–5V
Driver Leakage in Shutdown
Receiver Short-Circuit Current Slew Rate vs Load Capacitance
TEMPERATURE (°C)
0.1
LEAKAGE CURRENT  ( µA)
10
100
1780 • G08
1
–55 0 50 75
–25 25 100 125
V
OUT
= –30V
V
OUT
= 30V
Driver Short-Circuit Current
TEMPERATURE (°C)
–55
SHORT-CIRCUIT CURRENT (mA)
20
25
30
25 75
1780 • G09
15
10
–25 0 50 100 125
5
0
ISC+
ISC–
TEMPERATURE (°C)
–55
0
SHORT-CIRCUIT CURRENT (mA)
20
50
050 75
1780 • G10
10
40
30
–25 25 100 125
RX ISC
–
RX ISC
+
LOAD CAPACITANCE (nF)
0
SLEW RATE (V/µs)
12
16
4.0
1780 • G11
8
4
01.0 2.0 3.0 5.0
10
14
6
2
3.5
0.5 1.5 2.5 4.5
+SLEW
–SLEW
6
LT1780/LT1781
V
CC
: 5V Input Supply Pin. This pin should be decoupled
with a 0.1µF ceramic capacitor close to the package pin.
Insufficient supply bypassing can result in low output
drive levels and erratic charge pump operation.
GND: Ground Pin.
ON/OFF: A TTL/CMOS Compatible Operating Mode Con-
trol. A logic low puts the LT1780 in SHUTDOWN mode.
Supply current drops to zero and both driver and receiver
outputs assume a high impedance state. A logic high fully
enables the device.
V
+
: Positive Supply Output (RS232 Drivers).
V
+
≈ 2V
CC
– 1.5V. This pin requires an external charge
storage capacitor C ≥ 0.1µF, tied to ground or V
CC
. Larger
value capacitors may be used to reduce supply ripple. With
multiple transceivers, the V
+
and V
–
pins may be paralleled
into common capacitors.
V
–
: Negative Supply Output (RS232 Drivers).
V
–
≈ –(2V
CC
– 2.5V). This pin requires an external charge
storage capacitor C ≥ 0.1µF. Larger value capacitors may
be used to reduce supply ripple. With multiple transceiv-
ers, the V
+
and V
–
pins may be paralleled into common
capacitors.
TR1 IN, TR2 IN: RS232 Driver Input Pins. These inputs are
TTL/CMOS compatible. Inputs should not be allowed to
float. Tie unused inputs to V
CC
.
TR1 OUT, TR2 OUT: Driver Outputs at RS232 Voltage
Levels. Driver output swing meets RS232 levels for loads
up to 3k. Slew rates are controlled for lightly loaded lines.
Output current capability is sufficient for load conditions
up to 2500pF. Outputs are in a high impedance state when
in SHUTDOWN mode or V
CC
= 0V. Outputs are fully short-
circuit protected from V
–
+ 30V to V
+
– 30V. Applying
higher voltages will not damage the device if the overdrive
is moderately current limited. Short circuits on one
output can load the power supply generator and may
disrupt the signal levels of the other outputs. The driver
outputs are protected against ESD to IEC-1000-4-2
Level 4 discharges.
REC1 IN, REC2 IN: Receiver Inputs. These pins accept
RS232 level signals (±30V) into a protected 5k terminat-
ing resistor. The receiver inputs are protected against ESD
to
IEC-1000-4-2 Level 4
discharges. Each receiver pro-
vides 0.4V of hysteresis for noise immunity. Open receiver
inputs result in a logic high receiver output state.
REC1 OUT, REC2 OUT: Receiver outputs with TTL/CMOS
Voltage Levels. Outputs are in a high impedance state
when in SHUTDOWN mode to allow data line sharing.
Outputs are fully short-circuit protected to ground or V
CC
with the power ON, OFF or in the SHUTDOWN mode.
C1
+
, C1
–
, C2
+
, C2
–
: Commutating Capacitor Inputs.
These pins require two external capacitors C ≥ 0.1µF: one
from C1
+
to C1
–
and another from C2
+
to C2
–
. C1 should
be deleted if a separate 12V supply is available and
connected to pin C1
+
. Similarly, C2 should be deleted if a
separate –12V supply is connected to pin V
–
.
PI FU CTIO S
U
UU
7
LT1780/LT1781
ESD PROTECTIO
U
The RS232 line inputs of the LT1780/LT1781 have on-chip
protection from ESD transients up to ±15kV air gap and
±8kV contact tested to IEC-1000-4-2 test methods. The
protection structures act to divert the static discharge
safely to system ground. In order for the ESD protection to
function effectively, the power supply and ground pins of
the circuit must be connected to ground through low
impedances. The power supply decoupling capacitors and
charge pump storage capacitors provide this low imped-
ance in normal application of the circuit. The only con-
straint is that low ESR capacitors must be used for
bypassing and charge storage. ESD testing must be done
with pins V
CC
, V
L
, V
+
, V
–
, and GND shorted to ground or
connected with low ESR capacitors.
Operation Using 5V and 12V Power Supplies
1780 • ESD TC
0.1µF
RS232
LINE PINS
PROTECTED
TO IEC-1000-4-2
LEVEL 4
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
0.1µF
0.1µF
0.1µF
NC
C1
+
V
+
C1
–
C2
+
C2
–
V
–
DR2 OUT
LT1780
0.1µF
ON/OFF
5V V
CC
GND
DR1 OUT
RX1 IN
RX1 OUT
DR1 IN
DR2 IN
RS232 
LINE PINS 
PROTECTED 
TO IEC-1000-4-2
LEVEL 4
RX2 IN RX2 OUT
ESD Test Circuit
5k
5k
0.1µF0.1µF
LOGIC
INPUTS
LOGIC
OUTPUTS
ON/OFF 18
10
13
11
12
6
5
4
2
16
9
14
8
15
7
3
17 5V INPUT
–12V
OUT
RS232 OUTPUT
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
1780/81 • TA03
LT1780
12V INPUT
U
TYPICAL APPLICATIO
8
LT1780/LT1781
N Package
16-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
N Package
18-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
N16 1197
0.255 ± 0.015*
(6.477 ± 0.381)
0.770*
(19.558)
MAX
16
12345678
910
11
12
13
14
15
0.020
(0.508)
MIN
0.125
(3.175)
MIN
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
0.045 – 0.065
(1.143 – 1.651)
0.018 ± 0.003
(0.457 ± 0.076)
0.100 ± 0.010
(2.540 ± 0.254)
0.009 – 0.015
(0.229 – 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.325 +0.035
–0.015
+0.889
–0.381
8.255
()
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
N18 1197
0.020
(0.508)
MIN
0.125
(3.175)
MIN
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
0.045 – 0.065
(1.143 – 1.651)
0.018 ± 0.003
(0.457 ± 0.076)
0.005
(0.127)
MIN
0.100 ± 0.010
(2.540 ± 0.254)
0.255 ± 0.015*
(6.477 ± 0.381)
0.900*
(22.860)
MAX
18
123456789
1011
121314
16 1517
0.009 – 0.015
(0.229 – 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.325 +0.035
–0.015
+0.889
–0.381
8.255
()
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
9
LT1780/LT1781
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
SW Package
16-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
S16 (WIDE) 0396
NOTE 1
0.398 – 0.413*
(10.109 – 10.490)
16 15 14 13 12 11 10 9
12345678
0.394 – 0.419
(10.007 – 10.643)
0.037 – 0.045
(0.940 – 1.143)
0.004 – 0.012
(0.102 – 0.305)
0.093 – 0.104
(2.362 – 2.642)
0.050
(1.270)
TYP 0.014 – 0.019
(0.356 – 0.482)
TYP
0° – 8° TYP
NOTE 1
0.009 – 0.013
(0.229 – 0.330) 0.016 – 0.050
(0.406 – 1.270)
0.291 – 0.299**
(7.391 – 7.595)
× 45°
0.010 – 0.029
(0.254 – 0.737)
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
10
LT1780/LT1781
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
SW Package
18-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
S18 (WIDE) 0396
SEE NOTE
0.447 – 0.463*
(11.354 – 11.760)
15 14 13 12 11 10
16
9
12345678
0.394 – 0.419
(10.007 – 10.643)
1718
0.037 – 0.045
(0.940 – 1.143)
0.004 – 0.012
(0.102 – 0.305)
0.093 – 0.104
(2.362 – 2.642)
0.050
(1.270)
TYP 0.014 – 0.019
(0.356 – 0.482)
TYP
0° – 8° TYP
NOTE 1
0.009 – 0.013
(0.229 – 0.330) 0.016 – 0.050
(0.406 – 1.270)
0.291 – 0.299**
(7.391 – 7.595)
× 45°
0.010 – 0.029
(0.254 – 0.737)
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
11
LT1780/LT1781
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
S Package
16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.016 – 0.050
0.406 – 1.270
0.010 – 0.020
(0.254 – 0.508)× 45°
0° – 8° TYP
0.008 – 0.010
(0.203 – 0.254)
12345678
0.150 – 0.157**
(3.810 – 3.988)
16 15 14 13
0.386 – 0.394*
(9.804 – 10.008)
0.228 – 0.244
(5.791 – 6.197)
12 11 10 9
S16 0695
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
TYP
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH 
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD 
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
12
LT1780/LT1781
17801f LT/TP 0498 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1998
U
TYPICAL APPLICATIO
Supporting an LT1039 (Triple Driver/Receiver)
30k
30k
RS232 OUTPUT
RS232 OUTPUT
RS232 INPUT
RS232 INPUT
1780/81 • TA04
LT1039
TTL INPUT
30k
RS232 INPUT
V
CC
TTL INPUT
TTL INPUT
TTL OUTPUT
TTL OUTPUT
TTL OUTPUT
ON/OFF
RS232 OUTPUT
5k
RS232 OUTPUT
RS232 INPUT
LT1780
TTL INPUT
5k
RS232 INPUT
V
CC
TTL INPUT
TTL OUTPUT
TTL OUTPUT
ON/OFF
RS232 OUTPUT
1µF
2
4
1µF
5
6
3
7
18 17
1µF 1µF
GND
16
GND
10
V
+
V
–
1
9
18 17
5V
SHUTDOWN
C2
–
C2
+
C1
–
C1
+
V
+
V
–
11
12
13
10
15
14
9
8
12
14
16
11
13
15
7
5
3
8
6
4
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1137A 3Driver/5Receiver RS232 Transceiver IEC-1000-4-2 Level 4 ESD Compliance
LTC1383 5V Low Power RS232 2Driver/2Receiver Transceiver Low Supply Current I
CC
= 220µA
LTC1387 Single 5V RS232/RS485 Multiprotocol Transceiver Configurable as Dual RS232 or Single RS485 Transceiver
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com